After a day of training, I finally have an adequate army to attack level 8 wildernesses. I am however using a Dragon Heart item that boosts my troops attack by 20%, just to be safe. I have 6 more of them, so I figure why not use them.
I attacked a level 8 mountain next to my city and then moved on to level 8 lakes. So far, I've attacked 3 level 8 lakes and haven't had an egg drop, but I'll keep sending attacks until I can get my 2nd city. Below is an example of the army I am using to attack level 8 wildernesses. I am noticing that I'm losing a few Battle Dragons with each attack, so I may only do a few more until I have another batch of troops trained.